The invention provides a collapsible seat suitable for forming from a sheet material. The seat includes a seat panel, a back panel linked to the seat panel along a first fold line, and a support panel linked to one side of the back panel via a first web defined by second and third fold lines. The support panel is adapted to be linked to another side of the back panel via a second web partially defined by a fourth fold line. The seat also includes a reinforcement panel having one end linked to the support panel along an eighth fold line and an opposite end. The reinforcement panel is adapted to be positioned generally horizontally and under the seat panel in use. The reinforcement panel includes twelfth and thirteenth fold lines intermediate the seventh fold line and the support panel such that the reinforcement panel is divided into first, second and third portions. The first and third portions are substantially identical in size.